<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>变成CSS3的盒子</title>
    <style>
        div {
            width: 100px;
            height: 100px;
            background-color: pink;
            border: 20px solid #000;
            padding: 20px;


            /* 变成CSS3的盒子模型，好处固定了样式里面的设置的宽高和内边距，
            不需要进行手动减值 */
            box-sizing: border-box;
        }
    </style>
</head>
<body>
    <div>
        文字
    </div>
</body>
</html>